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Voltage and current are two different things.

Voltage is potential energy per charge, in joules per coulomb, while current is charge transfer rate, in coulombs per second. Its that same as saying that a battery has voltage but no current, because there is no load. Well, a capacitor resists a change in voltage by requiring a current to change the voltage. Once that voltage is achieved, there is infinite resistance to the voltage, and thus no current.

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Q: How could a capacitor have voltage but no current?
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Does voltage matter when charging a capacitor?

Yes, voltage matters when charging a capacitor. Capacitor charge rate is proportional to current and inversely proportional to capacitance. dv/dt = i/c So, voltage matters in terms of charge rate, if you are simply using a resistor to limit the current flow, because a larger voltage will attempt to charge faster, and sometimes there is a limit on the current through a capacitor. There is also a limit on voltage across a capacitor, so a larger voltage could potentially damage the capacitor.


What is the value of capacitor voltage and current after 5 time constant?

After 5 time constants, capacitor voltage/current will be about 99.3% of the input step change.


Why capacitor oppose change in voltage and allows current to flow?

Because that is what a capacitor does, resist a change in voltage. It holds a certain amount of energy per charge (voltage), and to change that voltage requires current proportionally to the capacitance.


Why current leading in capactor?

In the ac waveform of a capacitor the current waveform leads the voltage waveformcurrent is large to start until capacitor fills with it's voltage charge if that helpsAnswerThe terms 'leading' and 'lagging', used when describing power factor, are defined in terms of whether the load current is leading or lagging the supply voltage.In a capacitive circuit, the load current leads the supply voltage, so the power factor is leading.


Why does the current lead the voltage across a capacitor by 90 degree rather than lag it?

A: Because a capacitor have to have time to charge to the voltage In a capacitor, the current depends on the voltage difference across it. On AC, this makes it charge, if the voltage is increasing above zero, and discharge if the voltage is reducing towards zero. Because a capacitor has almost no internal resistance, and most loads that it is connected to have only very small resistances in series with the capacitor, the charging and discharging currents depend pretty much on the rate at which the voltage is changing. At the zero crossing point of the sine-wave, when the voltage is actually zero, the rate of change of voltage is very high (the sine-wave is at its steepest), so the current is also very high. If the voltage is positive-going, the current is positive, and if the voltage is negative-going, the current is negative. At the peak of the voltage waveform, the rate of change of voltage is zero or very low (the sine-wave is flat, and not really changing its voltage) so the current is zero, too. Since the maximum positive current occurs when the voltage is passing through zero, going positive, and the maximum negative current happens when the voltage is passing through zero, going negative, the current peaks happen 90 degrees before the voltage peaks, so the current is said to lead the voltage. This is the same as saying the voltage lags the current by 90 degrees.

Related questions

Does voltage matter when charging a capacitor?

Yes, voltage matters when charging a capacitor. Capacitor charge rate is proportional to current and inversely proportional to capacitance. dv/dt = i/c So, voltage matters in terms of charge rate, if you are simply using a resistor to limit the current flow, because a larger voltage will attempt to charge faster, and sometimes there is a limit on the current through a capacitor. There is also a limit on voltage across a capacitor, so a larger voltage could potentially damage the capacitor.


Relation between voltage and current if you consider capacitor ckt?

In a capacitor ckt, current will be lead ahead from voltage by an angle 90 degree. Because for a capacitor the relationship between voltage and current is given as v=(jx)i , where v= voltage i= current jx=capacitive reactance


What happens to the current in a circuit as a capacitor charges?

What happens to the current in a circuit as a capacitor charges depends on the circuit. As a capacitor charges, the voltage drop across it increases. In a typical circuit with a constant voltage source and a resistor charging the capacitor, then the current in the circuit will decrease logarithmically over time as the capacitor charges, with the end result that the current is zero, and the voltage across the capacitor is the same as the voltage source.


How can you double current into a capacitor?

increasing voltage


What is the value of capacitor voltage and current after 5 time constant?

After 5 time constants, capacitor voltage/current will be about 99.3% of the input step change.


What does the continuity of capacitor voltage mean?

It might mean that the voltage across a capacitor cannot change instantanteously because that would demand an infinite current. The current in a capacitor is C.dV/dt so with a finite current dV/dt must be finite and therefore the voltage cannot have a discontinuity.


Why capacitor oppose change in voltage and allows current to flow?

Because that is what a capacitor does, resist a change in voltage. It holds a certain amount of energy per charge (voltage), and to change that voltage requires current proportionally to the capacitance.


What effect does the series resistance of a capacitor used in a capacitor filter have on diode current and ripple voltage compared with an ideal capacitor of no resistance?

The effective resistance of the capacitor reduces the ripple current through the capacitor making it less effective in its function of smoothing the voltage. But if the capacitor filter is fed by a transformer and diodes, the resistance of the transformer exceeds that of the capacitor.


Why current leading in capactor?

In the ac waveform of a capacitor the current waveform leads the voltage waveformcurrent is large to start until capacitor fills with it's voltage charge if that helpsAnswerThe terms 'leading' and 'lagging', used when describing power factor, are defined in terms of whether the load current is leading or lagging the supply voltage.In a capacitive circuit, the load current leads the supply voltage, so the power factor is leading.


Does a capacitor store energy in form of an magnetic field?

Current stops going into a capacitor when it's voltage is equal to the supply voltage. From then there is no flow of current, so there is no magnetic field. Yet the capacitor remains charged and has energy to release if required.


What is the phase relationship of voltage across a capacitor and current though the capacitor?

In a capacitor, the current LEADS the voltage by 90 degrees, or to put it the other way, the voltage LAGS the current by 90 degrees. This is because the current in a capacitor depends on the RATE OF CHANGE in voltage across it, and the greatest rate of change is when the voltage is passing through zero (the sine-wave is at its steepest). So current will peak when the voltage is zero, and will be zero when the rate of change of voltage is zero - at the peak of the voltage waveform, when the waveform has stopped rising, and is about to start falling towards zero.


Why does the current lead the voltage across a capacitor by 90 degree rather than lag it?

A: Because a capacitor have to have time to charge to the voltage In a capacitor, the current depends on the voltage difference across it. On AC, this makes it charge, if the voltage is increasing above zero, and discharge if the voltage is reducing towards zero. Because a capacitor has almost no internal resistance, and most loads that it is connected to have only very small resistances in series with the capacitor, the charging and discharging currents depend pretty much on the rate at which the voltage is changing. At the zero crossing point of the sine-wave, when the voltage is actually zero, the rate of change of voltage is very high (the sine-wave is at its steepest), so the current is also very high. If the voltage is positive-going, the current is positive, and if the voltage is negative-going, the current is negative. At the peak of the voltage waveform, the rate of change of voltage is zero or very low (the sine-wave is flat, and not really changing its voltage) so the current is zero, too. Since the maximum positive current occurs when the voltage is passing through zero, going positive, and the maximum negative current happens when the voltage is passing through zero, going negative, the current peaks happen 90 degrees before the voltage peaks, so the current is said to lead the voltage. This is the same as saying the voltage lags the current by 90 degrees.